In medical technology, particularly in diagnostics, bodily fluid samples are often preconditioned so that it is possible to perform a diagnosis on the basis of the constituents of the samples. The constituents of the bodily fluid samples must often be separated for this purpose, with filters often being used for this.
An example relates to separating blood plasma from whole blood. Blood cells can be filtered out of a blood stream with the aid of a filter membrane while the blood plasma can pass the filter membrane. Lab-on-chip (LOC) systems offer the advantage of ensuring an automated progress of diagnostic assays such that operating errors can be minimized. Such systems moreover lower the costs of the analysis procedure because smaller sample volumes can be analyzed in a very short time.
By way of example, an LOC system is proposed in the article VanDelinder, V., Groisman, A., Anal. Chem. 2006, 78, 3765, in which blood plasma can be separated out of whole blood with the aid of cross-flow filtration through a microstructured sieve.
The document US 2008/0128341 A1 teaches a micro-filtration system, in which whole blood is pumped through a microstructure in a microchannel, and so merely the blood plasma can pass the microstructure.
The document US 2009/0120865 A1 discloses a multi-layered substrate with an embedded filter unit, in which the blood plasma can be separated from whole blood.